Vikernes was a member of the notorious Norwegian black metal band Mayhem, and is known for the fatal stabbing of a band-mate and setting fire to several churches in the early 1990s.

Musicians and fans of black metal often express anti-Christian views and some were involved in the burning of more than 50 churches in Norway between 1992 and 1996.

Key points

Musician Kristian Vikernes arrested over suspected terrorist plot.

He was previously a member of the prominent black metal band Mayhem.

Jailed after stabbing death of band-mate Øystein Aarseth.

He was also known to have burned down several Norwegian churches.

Had links to Norwegian mass killer Anders Behring Breivik.

Vikernes was sentenced to 21 years in prison following the murder of Mayhem band-mate Øystein Aarseth, who was also known as Euronymous.

He was released after serving 16 years, and later settled in France in 2010.

"The stay in prison probably made me a little more extreme, in every way," he said in a 2010 interview with the magazine Guitar World.

That same year on his blog, he called on people to vote for Marine Le Pen, the leader of France's far-right National Front party.

He had been under surveillance for several years, but anti-terrorism authorities in Paris opened a probe into the father-of-three at the beginning of the month after his wife purchased weapons - legally, as she has a permit.

Officers seized several weapons at their home on Tuesday, including four .22 calibre Long Rifles.

Minister says weapons purchase showed 'terrorist plan was possible'

Mr Valls said authorities had decided it was important to arrest Vikernes "to act before and not afterwards."

"The DCRI (French domestic intelligence service) considered that messages he had posted on the internet expressed huge violence," he said.

"The purchase of weapons and cartridges by his wife showed that a terrorist plan was possible. To know more, to know what this plan could be... the DCRI considered it was important to arrest and question him."

Vikernes once had a link with Breivik, who is being held in isolation in a high security prison near Oslo for killing 77 people in twin attacks in 2011, Mr Valls said.

He said the notorious mass killer had sent Vikernes a long manifesto that he had worked on for years and which he published just before the Norway attacks.

Neighbours say Vikernes polite, normal, nice

The mayor of Salon-la-Tour said Vikernes had settled in a rented house a year ago with his family, away from the village.

Jean-Claude Chauffour said the couple met several years ago when Cachet was graduating from high school.

"He doesn't speak French very well," Chauffour said, adding that the family had three children and Cachet was pregnant with her fourth. It is unclear whether all the children are the musician's.

The young woman's mother appears to have taken care of their children, who did not go to school, the mayor said.

Meanwhile a shocked neighbour of the couple, Yves Langoile, said Vikernes was "polite" and "appeared to be normal and nice", and close to his children.